<!DOCTYPE html>
<html lang="zh" style="font-size: 100px;">
<head>
	<meta charset="UTF-8" />
	<!--<meta name="viewport" content="width=device-width, initial-scale=1.0" />-->
	<meta name="viewport" content="width=device-width,minimum-scale=1.0,maximum-scale=1.0,user-scalable=no">
	<meta http-equiv="X-UA-Compatible" content="ie=edge" />
	<title>Document</title>
	<style type="text/css">
		body {
			font-size: 16px;
		}
		div {
			background: green;
			margin-top: 10px;
			font-size: 20px;
			color: #fff;
		}
		.a {
			height: 100px;
		}
		.b {
			font-size: 30px;
			height: 1em;
		}
		.c {
			height: 1rem;
			width: 1.3rem;
		}
		.d {
			width: 2.5rem;
			height: 0.8rem;
		}
	</style>
</head>
<body>
	<div class="a">
		px
	</div>
	<div class="b">
		em
	</div>
	<div class="c">
		
	</div>
	<div class="d">
		宽250px,高80px
	</div>
	
</body>
</html>